Conventional door framing requires at least two door hinges secured onto a door and a door frame. Since each of the two hinges is individually secured to the door and the frame, they therefore form separate turning axes more or less different from each other. As a result the door does not swing smoothly and exactly in a single axis.
Employing one pair of the well known type door hinges will cause difficulty in the door swinging. However, when employing the hinges disclosed in two prior applications of the same petitioner, Ser. No. 907,860 titled Self-Closing Hinge or Ser. No. 946,057 titled Bilateral Swingable Self-Closing Hinge, difficulty may exist not only in the door swinging but also in getting the door to be self-closing.
Both hinges of the two prior applications mentioned above feature at least one steel ball residing in a circular undulating groove in the joining axle part, and when the door opens the ball (or balls) rolls up on the up-going slope of the groove and soon after that the ball is (or balls) forced to roll down by the gravitation force of the door and then the door self-closes. But when one pair of hinges of the kind disclosed in the two prior applications are employed to frame a door and are not fixed in a single turning axis line will cause the two ball of the individual hinges not to roll synchroniously on the respective grooves and might cause swing of the door to be blocked.
Furthermore, the employing of one each ball in each groove of the each hinge of the prior application makes the ball (or balls) support the door in an unbalanced manner in the joining axle of the hinge and produces much friction between the ball or the ball receiver (the socket of the joining axle part) and the axle bolt (also the grooved body), and therefore might make door turning difficult.